Process for recovering mercury.



C. H.' FULTON.

" PROCESS FOR RECOVERING MERCURY.

APPLICATION FILED APR. 2l, IBI?.

man@ Apu 30,1918.-

I I I I I EWW , briquet of novel'composition for use in av CHARLES H, FULTON, OF S'l. LOUIS, MISSOURI, ASSIGNOR, BY MESN E ASSIGNMENTS, TO

METALLURGICAL LABORATORIES, INCORPORATED, 0F CHIGAGO,` ILLINOIS, A COR- IRATION OLE' ILLINOIS.

PROCESS FOR RECOVERING MERCURY.

Specification of Letters Patent.

rateateu apr. so, raie.

Application led April 21, 1917. Serial No. 163,598.

To all whom it may concern: s,

Be it known that I, CHARLES, II. FULTON, a citizen of the United States, residing at St. Louis, Missouri, have invented a certain new and usefullmprovement in Processes for Recovering Mercury, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

`This invention relates to the recovery of mercury from its ores and 'from material containing mercury.

'Ihe main object of the invention is to provide a practicable process for recovering mercury from its ores and other mercury bearing material; that can be accurately controlled; that reduces the cost of recovering mercury and which can be practised in an apparatus of simple design operated 'by a few operatives. 4

.Another object is to provide a mercury distilling apparatus.

Brieiiydescribed, my process consists in forming mercury ore lor mercury-bearing material into objects that will substantially retain their original form and volume when heated to a ldistilling temperature, subjecting said objects to 'heat in a distilling apparatus, so as to convert the mercury in same into vapor, and thereafter' treating the mercury vapor in a condenser, so as to convert it into liquid form.

It is immaterial, so far as Amy broad idea is concerned, how said .objects are formed, but I prefer to form them by combining finely-divided mercury ore or mercury-bearing material, a porous substance, a reducing agent or reagent and a binding material mixed in certain proportions, and thereafter forming said mixture into solid objects or briquets under high pressure. The distilling operation can be effected either in a furnace heated by carbonaceous fuel or in an electric distilling furnace. Then an electric distillingfurnace is used it is neces- Sary to incorporate in the objects or briq uets, preferably during the operation of orming same, a material or substance that is a conductor of electricity. ld`inely-divided coke is particularly well adapted for this purpose, as it is porous and it is also a good electrical conductor. It also serves `as a re ducing agent if the mercury is in the form of oxid. I prefer to use a carbonaceous binding material, such, for example, as tar or hard coal tar pitch, as I have found that briquets formed from finely-divided material containing mercury, finely-divided coke, a reagent or reducing agent and a carbonaceous binder mixed in certain proportions remain intact and preserve their form and volumewhen they are subjected to a distilling temperature. Any substance that will desulurize or absorb the sulfur of the mercury sulid may be used as the reagent, such, for example, as any one of the oxids of iron, lime or metallic iron :in `the shape of filings. I prefer, however, to use a hematite or limonite ore containing a high percentage of iron. It is preferable to heat the mixture or add the binder in a molten state to the, other ingredients during the process of forming the briquets, so as to "ca'usethe particles of the various ingredients to bedoiiic thoroughly coated with the binder. and while I prefer to use hard coal tar pitch as the binder, any other suitable carbonaceous material may be used in place of hard -coal tar pitch. ther 'porous substances than coke may also be used, but it is preferable to use coke, as it contains no volatile matter to be driven off preliminary to distillation; it gives rise to no deleterious gases during the distilling` operation, and

as its particles have assumed what may be considered their final i'orm at the time the coke 1s incorporated 1n the briquet, said particles will not break down during .the dis-- tilling operation, thus insuring the continued stability of the briquet during and afterthe distilling operation.

The shape of the briquets is immaterial, but in practice I form the -mixture into briquets of spherical, cylindrical or yother preferred form in molds, wherein they lare subjected to a pressure of between 500 lbs. and 1000 lbs. per square inch, so as to solidify the mixture and form it into a compact mass that will not swell and crack during 4the subsequent drying and IVhen a carlionaceous binding material is used' it is necessary to preheat the briquets after they have been removed from the molds, or just prior to the distillingf` operation, so as to drive oli the volatile matter in the bind ing material and convert said binding matedistilling operations.v

rial intocoke, thus eliminating the possibility of the mercury vapor being diluted by volatile hydrocarbons in the distilling operation. This preheating of the briquets also tends to make the briquets better electrical vconductors and is advantageous` if the briquets are electricallydistilled, as hereinafter described. In 4the preheating and drying operation just referred to it is desirable that t-he briquets be protected from the action of oxygen, so as to prevent the coke in the outer surface of the briquets from oxidizing and thus causing the outside of the briquets to assume a loose and friable condition, with resulting disintegration of the surface of the briquets.

The proportions of the coke and the mercuryl ore or mercury-bearing material should be such that a sufficient mass ofporous material will be left in the briquet after the distilling operation to maintain substantially the original volume of the briquet. The proportions, of course, will vary with different mercury ores or mercury-bearing materials, but I have found that satisfactory briquets can be produced from finely-divided ore or mercury-bearing material, finely-divided coke, varying from about l0 mesh'to 200 mesh, or finer, coal tar pitch and one of the oxidsnof iron mixed in approximately the following proportions: between 35 and 50%, by weight, of mercury ore or mercury-bearing material; between l5 and 20% iron oxid; between 30 and 40% coke and between 8% and 12% of pitch. The amount of binding material used also varies Withthe degree of fineness of the coke and thev ore or mercurybearing material, but sufficient binding material should be used to cause theparticles of the other ingredients to be completely surrounded by a film of binder `which will unite them into a coherent mass by its adhesive action when the briquets are first formed, and which, after the preheating of the briquets and coking of the binder, will permanently and firmly unite the particles of the other ingredients by means of the coked residue of the binder left-inthe briquets. The essential thing in respect to the iron oxid or other desulfurizin agent used is that there shall be enough to" take care of any sulfur that may be combined With the mercury in the ore or mercury- .fiows in bearing material, thus reacting with the sulfur when a temperature between 900o C. and 1000o C. is obtained in the briquet, liberating the" mercury vapor.

In making up such briquets the hard coal tar pitch, if that be the binder employed, is ground and mixed with the other ingredients until a uniform mixture is obtained. The mixture is then heated to the melting point of the pitch, which melts and place and thoroughly coats each particle o the various ingredients. Another L a i L way of 'combining the ingredlenits 1s to mix work the mixture cold. The mixture is then formed into briquets in suitable molds in which they are subjected to a high pressure,

preferably upward from 500 lbs. to the.

square inch. If soft coal tar pitch is used as the binder, then the mixed ore or mercurybearing material and the other ingredients are heated and the soft coal tar pitch, is heated above its melting point and added at a certain rate to the other heated ingredients. After the briquets have been removed from the molds they are preheated or dried for the purpose of driving off the volatile hydrocarbons of the binder. This is preferably done by subjecting the briquets, under reducing or non-oxidizing conditions, to a gradually rising temperature to about 400 C. I have found that when itch is employed as the binding material t 1e pitch will become coked at about 400 C. The briquets may be protected from the action of oxygen during the preheating operation b embedding them in finely crushed coke, y which they are completely covered and inclosed, or by preheating them in a chamber from which oxygen is excluded. A briquet produced in the manner above described consists practically of a coke matrix or cellular structure whosecells are filled with the substance that is to be distilled. This matrix or cellular structure is made up of the coke with which the ore or mercury bearing material is lirst mixed, and the coke left by the distillation of the pitch binder, and it is of such a charactei-'that it will maintain both its original form and volume during thel distilling operation and will serve as a proper resistor con-` ductor between the electrodes of an electric distilling furnace.

After the briquets have been formed in v' the "ljmner above described they are distilled in a distilling-furnace, "so as to cause the mercury in same to be driven ott' in the form of vapor, and thereafter said mercury vaporis admitted to al condenser, wherein itA is converted into li uid form. The briquets can either be distilled in a furnace lformed from a -rnember or retort Lacanau sectional view of an apparatus that can 'be used to practise my process.

Fig. 2 'is a top plan view of the bottom electrodes of the furnace on which the bri.n quet columns are arranged.

'F ig. 3 is a top plan view 'of the perforated supporting structure on which said eleci 'trodes rest; and

.F ig. 4t isa top plan view of the connectors that are arranged in engagement with the upper'ends of the briquet columns.

rlhe apparatus shown in the drawings comprises a vertically-disposed, hollow A. that is arranged on a base B, so as to form the c of an electric furnace, said member .A preferably being removably mounted on the base B, so that it can be lifted therefrom by a crane or other suitable device (not shown) and arranged in position on a second retort base B. A condenser D, which is provided with a base E, is arranged between the retort bases B and B1', said retort bases and condenser base being built of refractory material and preferably combined as a single or integral, structure, as shown in the drawings. 'lhe retort A is preferably steel shell l' heavily lined Withyrefractory and non-conducting material 2 and having its lower end open, the retort being provided at its upper end with a discharge opening 3 that is normally closed by a cover l formed .of refractory material. The retort base B is provided with a perforated supporting structure F formed of vrefractory material on which electrodes 5 and 6 are mounted, said supporting structure having numerous holes, spaces or passageways l0 in same, as shown in Fig. 3,' through which the products of thedistillation can escape from the distilling chamber C.V tf'the furnace is designed for A use 'with three-phase alternating current "connection of the "ti/type, theelectrode 6 will consistl ot athree-arrn neutral point electrode and the electrodesy 5 will consist of j mixture.

lsupply electric anfopening in the substantially .segmental shaped electrodes that are arranged between the arms of the vneutral point electrode 6, as shown in Fig. 2, the electrodes. 5 and 6 being preferably vformed from graphite or an ore-colrepitch rlhe graphite conductors .c that current tov the electrodes V5 are'led into the retort base B through openings therein, andl each of said conductors is connected at its inner end to a plug 'l1` of conductingmaterial that is arranged in supporting structure i4,

" the upper ends of said conducting plugs ll contacting with the electrodes 5 that rest upon the supporting structure .Briquets of the composition and character previously described have a siecitic resistance of about .03 ohms per cu ic inch, and when a number of such briquets are arbriquet columns together.

listilling chamber.

Agreat onto() small tricdstilling furnace so as to form a lined resistor, the resistance of the resistor may be readily calculated by the cross section of the briquets, lthe height and number of` the briquet columns in the distilling chamber and the manner of connecting' the '(lhe briquets can be made in the form of comparatively short, cylindrical shaped objects, a number of which `can be superimposed one upon the other to form vertical column, or each briquet can consist of a comparatively long object. ln setting up a charge in a furnace of the design herein illustrated twelve briquet columns W are arranged in six pairs on the electrodes 5 and 6, the neutral point electrode G supporting six columns and each of tbe-electrodes 5 rllhereafter, conductors 13 of the form shown in Fig. 4 .are arranged in engagement with the upper endsof the Abriquet columns lV, so as to electrically connect the tops of two adjacent pairs of briquet columns. the briquets have been set up and connected together in the manner described the retort A isI arranged in operative position on the base B over said briquet columns. the current is turned on the current c0nveyed to the, pair of briquet columns resting on the electrode 5 at the left'hand side of Fig. 2 will pass upwardly through said columns to the conductor 18 at the upper ends of same which electrically connects said col umns tothe briquet columns supported by the lower left hand arm of the electrode 6, thence downwardly through the briquet columns resting on said arm to the neutral point at the center of the electrode 6. The passage of the current for the other pairs of briquet columns is similarly all convergent on the neutral point of the gives the cmmon Y connection` of the alternating three-phase current. lt will, of course, be understood that it is immaterial, so far as my invention is concerned, how

the electric current is supplied to the briquet columns, so long as the electrical resistance is such' as' ment within the'charge itself to practically completely distil the `mercury therefrom.

y varying the through the briquet columns W the, speed of distillation may be kept under perfect control and the rate of distillation can be varied at will. The current-is preferablv supplied to the furnace through a transformerso designed as to supply current of different voltages. If the current is too at any given voltage, the voltage .ofthe transformer may be decreased or increased until the proper flow of current is obtained. rlhe reaction between cinnabar and the desulfurizing agents takes place between 900o C. and 10000 C., and

supporting two columns.l

electrode 6, which Aaa- When

tocause a sufficient heat developll amount o'f current sent mercury vapor is forced from the briquets. This vapor then passes to the condenser D through a passageway 14. The condenser D ofthe a paratus herein shown consists l furnace the retort is then raised by means of a crane or other suitable hoisting apparatus and the briquets discharged in a suitable manner. The retort A is carried to the other. retort base B', upon which briquets have been previously set up, and lowered into operative 'position over said briquets. The heat stored in the walls of the retort A is used to preheat Aand bake the raw briquets until they become good conductors of electricity, the volatile matter that is driven oii' during the preheating operation being allowed to escape through the opening 3 in the upper end of the retort that is normally closed by the cover 4, if it is considered undesirable to have said volatile matter pass through the condenser. After the briquets have been distilled they can be used again Ato form the conducting material or the desulfurizing or reducing reagent of new briquets until the distilled briquets become commercially valuable due to the continued concentration of valuable metals from thel ore, such as gold, platinum, silver, copper, lead or other metals of higherV volatilizing points than the one distilled or until the distilled briquets become Worthless, due to the concentration o f the gang of the ore.

A process of the character above described can be accurately controlled; it materially reduces the cost of treating mercury ores and mercury-bearing material, owing to the fact that the material being treated is in such form that it can be handled conveniently during the operations of charging the distilling furnace and removing the residue therefrom; andstill another desirable feature of said process lis that a distilling apparatus of great capacity can be used successfully to practice4 the process.

Having thus described my invention, what I claim, and desire' to secure by Letters Patent, is: f

1. A process for recovering mercury, charactci'ized by forming mercury ore or Inercury-bearing material into objects that will retain substantially their original form and jvoliiinc when subjected to a distilling teiliperaturc, heating said objects to convert the mercury in saine into vapor, and thereafter treating the mercury vapor so as to convert it into the form desired.

-2. A processfor recoverin mercury, characterized by combining fine y divided mercury ore or mercury-bearin material with a porous substance, a reducing agent or reagent anda 'bindinginateriah forming said mixture in t'o objects that will retain their approximately arigin'al form and volume when ysubjected to a `distilling temperature, heating said objects so as to drive off the mercury in the form of vapor, and thereafter converting said mercury vapor linto liquid form.

3. A process for recovering 'iii'.ercury, cha-racterized by combining finely divided mer.- cury ore or mercury-bearin material with finely divided coke and a car naceous bindin material, forming said mixture into briquets under pressure, suiiicient binding material beingused so as to insure the' briquets retaining their substantially original form and volume when they are subjected to a distilling temperature, heating said briquets so as to drive oif the volatile matter in the carboiiaceous binding material, and thereafter distilling the briquets.

4. A process for recovering mercury, which consists in forming briquets from a finely divided ore or mercury-bearing material, a porous substance, a reducing agent or reagent and a binding material mixed in such proportions that the briquets will retain their approximately original form and volume when they are subjected to a distilling temperature, heating said briquets in a distilling chamber so as to liberate the vapor in same, and thereafter condensing said mercury vapor.

5. Aprocess foi'.recoverin mercury characterized by combining finely divided mercury ore orv mercury-bearing material with other suitable substances so as to form a cellular structure capable of withstanding distilling temperatures and having its cells 0i' interstices containing metal, subjecting said cellular structure to heat in a distilling chamber so as to vaporize the mercury therein, and thereafter condensing said mercury vapor.

6. A process for recovering mercury, characterized by forming mercury ore or mercury-bearin material into an object that is an electrica conductoi then passing a current of electricity through said objects so as to heat it sufficiently to cause the mercury in same to vaporize, and collecting and condensing said mercury vapor.

7. A process for recovering mercury, characterized by forming mercury ore or mercury-bearing material into an electrical conducting object that will maintain its approxiinately original form and volume when I subjected to a distilling temperature, passing a current of electricity through said ob- 10. A briquet for use in distilling furject so as-to distil the mercury out of same, naces formed from finely divided mercury ore and thereafter collecting and condensing the or mercury-bearing material, finely divided mercury vapor evolved in the distilling opcoke, -a vbindingl material, and if necessary, 30 eration. 5 a reagent, mixed in sueh proportions that' 8. A process for recovering mercury, charthe briquet will retain its substantially origiactci'ized by forming mercury ore or mernal form and volume when subjectedto a cury-bearing` material into briquets that will dietilling temperature.

retain their approximately yoriginal formv ll. A briquet for use in distilling fur- 35v and volume ivhen subjected to'a distilling naces` consistingv of a compressed object conitemperature. interposing one or more of prising a cellular portion `toi'ined of consaid briquets as a continuous resistor be'- ducting' material and havingits cells or 11itiveenthe electrodes of an electric furnace tersticeel filled with tinelv divided lmercury and passing a current otI electricity through ore or merelii' vbeai'ing' material. 40 them to lient the briquets to a distilhng teniv1;). A briquet for use in dietillinze` furperature, and thereaftercondensing the mernacee. eonsisting ot' a compressed object, cury vapoi' evolved by the distillingY operacomposed oi ,finely divided'mercury ore or tion. i v l niereni'y-lcaring material, finelyr divided briquet t'or use in a distilling t'nreolce. a reducing agent or reagent and thel nace eomposed of mercury ore `or mercury eolted residue oi :i earbonaeeous binder, bearing i'nateriaLa porous substance, a remixed in .auch pi'opoitionh` that the briquet ducinjdr agent or i'ean'ent and a binding niawill retain it.4 appifoxiinatelwv original i'orni ierial eonibined into a compact. mass that and vo'lnnie ivlien subjected to a diet-illingr will retain ite 4subestaiiliall'v original form temperature. and volume when lobjected toa distilling' temperature. CHARLES ll. FULTGN. 

